Camera-based vital signs monitoring can measure heart-rate, respiration and oxygenation, SpO2 values and actigraphy unobtrusively from a distance. Traditional contact sensors for measuring heart-rate, respiration, SpO2 and actigraphy are attached to the subject (i.e. a living being, particularly a human being like a person, but possibly also an animal). Inherently the vital signs values produced by these sensors are associated with a subject ID, i.e. an identifier of the subject that uniquely identifies the subject. For instance, in a hospital environment, from day one on which a patient is in the hospital the nurse attaches the sensor to the patient, and the measured vital signs are then associated to the patient's name and bed number. One of the main advantages of camera-based vital signs monitoring over on-body sensors is the high ease-of-use since there is no need to attach a sensor to the living being, but the camera just needs to be directed to the living being.
Since camera-based vital signs monitoring is performed in a contactless way, it is unclear how to associate the values measured to the identity of the subject. As an example, in hospitals no system is able to detect that the vital signs measured from one patient lying in a bed at time t0 are still the vital signs of that same patient at time t0+t. A new patient might be there or patients might have voluntarily/involuntarily exchanged their beds.
Due to the constant patient flow, it is not desirable to have a fixed association based on patient's bed location. This could clearly lead to a confusion of medical data which is not acceptable. It is also not a preferred solution to attempt to “track” a patient based on its vital parameters only because of the extremely high probability of mismatch with another patient. Due to the limited range of values of the vital signs measured is very likely to find two persons having at one point in time the same parameters. Further, identification based on vital signs is considered unsuitable in many application due to the fact that the evolving health condition, e.g. of a patient in a hospital, changes the vital signs, making them less suitable for identification of the patient.